Emergency governor exerciser



1970 N. E. NUTTER 3,508,443

EMERGENCY GOVERNOR EXERCISER Filed June 20; 1968 INVENTOR NORMAN E.NUTTER,

BY 40. Q. ms ATTORNEY.

United States Patent US. Cl. 73-509 4 Claims ABSTRACT OF THE DISCLOSUREA device for exercising or testing an emergency governor by injectingpressurized fluid inside the rotating governor cavity from a plungerarranged to move against the end of the governor shaft. Pressure buildsup within the governor causing the governor to be exercised.

BACKGROUND OF THE INVENTION Prime movers, such as steam turbines, aregenerally supplied with an emergency overspeed governor ,to trip anoverspeed mechanism and shut down the prime mover in the event ofoverspeed. Since such occurrences are relatively rare, it is desirableto provide a device to periodically test or exercise the overspeedgovernor to insure that it is in proper working order. Many systems havebeen devised for exercising the emergency governor while the prime moveris running without actually tripping out or overspeeding the primemover, examples of such systems being seen in US. Patents 2,926,680,Eggenberger; 2,998,- 017, Cavalieri; and 3,342,194, Dwight, all assignedto the present assignee.

All of the foregoing patents employed an emergency governor whichincorporated a ring or bolt with an offcenter cavity for exercising thegovernor. Introduction of hydraulic fluid into the cavity created anadded off-center mass which tended to move outward due to thecentrifugal force of rotation, thereby creating an artificial overspeedcondition in so far as the governor was concerned. This type of testingmechanism is well known and exemplified by US. Patent 1,666,490, Dryer,assigned to the present assignee.

One of the shortcomings of the foregoing type of governor exerciser isthat the centrifugal force on the'oilfilled cavity is dependent upon thespeed of rotation. Therefore, the testing mechanism becomes lesseffective with reduced speeds. This caused the testing mechanism tobeless useful on variable speed turbines.

It has been suggested in the prior art that the oil dump type 'ofemergency governors can also be tested by dumping or evacuating apressurized governor cavity, as shown in US. Patent 3,026,891, Hoffman,but such testing devices are based upon a system involving normal oilpressure within the governor cavity for normal overspeed op: eration andusually re'quiresome type'of rotating-seal;

Accordingly, one object of the present invention is to provide animproved emergency governor exerciser which enables testing theemergency governor over a wider range of prime mover operating speedsthan with previous designs.

Another object of the invention is to provide an improved device forexercising an emergency governor of the olf-center bolt type with apressurizing fluid.

DESCRIPTION OF THE DRAWING The subject matter which is regarded as theinvention is particularly pointed out and distinctly claimed in theconcluding portion of the specification. The invention, however, both asto organization and method of practice, together with further objectsand advantages thereof, may best be understood by reference to thefollowing description, taken in connection with the accompanyingdrawing, in which the single figure of the drawing is a sectionaldetailed view of the emergency governor exerciser.

SUMMARY OF THE INVENTION Briefly stated, the invention is practiced byproviding a piston area on a spring-biased off-center bolt and an inletport through the shaft to the rotating governor cavity. A spring-biasedorificed plunger is disposed to move against the inlet port and injectpressurized fluid therethrough to move the off-center bolt to a trippingposition. The pressurizing fluid also provides a lubricating function toreduce wear between shaft and plunger.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawing, the end of arotating shaft member 1 is arranged to incorporate an emergency governor2 which actuates a trip lever 3 in the event of overspeed. Otherdevices, not shown, and not material to the present invention, bring theshaft 1 to rest and may include provi s'ion for resetting the trip lever3.

The emergency governor 2 may take various forms but as shown herecomprises an off-center bolt 4, slidably disposed in members 5, 5a.Members 5, 5a are threaded into either end of a hole through the shaftso that they may be adjusted to set the biasing force of a spring 6 andto balance the device.

The threaded members 5, So also close off either end of the hole throughshaft 1 to define a chamber 7. An access hole 8 to chamber 7 ispreferably located on the shaft centerline and the shaft end 9 ismachined to a flat or planar surface. The off-center bolt 4 includes apiston area 10 exposed to chamber 7 and located on the same side of theshaft centerline as the eccentrically disposed center-of-mass 11.

Other devices (not shown and not material to the present' invention) arearranged to deactivate the normal prime mover trip system when theexerciser is actuated. These may be systems as described in theaforementioned Eggenberger, Cavalieri and Dwight patents. It will beunderstood that actuation of lever 3 by the exerciser to be describedwill not actually shut down the prime mover, which may be running whileexercising takes place.

A pressurized fluid injector, shown generally at 12, is

disposed close to the end of shaft 1. The injector comprises astationary body 13 with a bore 14 coaxial with theshaft centerline. Aninjector plunger 15 is held slidably disposed in the bore by means of aland 16 and a collar 17. It is lightly biased to the seated positionshown by means of a spring 18. The plunger includes an access hole 19 toits hollow interior and an outlet orifice 20 coaxial with the shaftcenterline.

The construction of the plunger 15 will vary somewhat with'design's butsuitable resultslhave been obtained with a"1 diameter plunger having a aorifice at 20. The face end 21 of the plunger is flat and disposed aboutA; of an inch from the shaft end 9.

Two intersecting halfmoon slots 23 are cut in the face 21 of theplunger. These extend outward beyond the diameter of access hole 8 inthe shaft so that oil will be supplied to the interface between surfaces9, 21. Auxiliary flow may be provided, if desired, by means ofadditional small holes, such as 24.

Means to provide a pressurized fluid for testing purposes include apressurized source, not shown, controlled by a valve 25 and an actuator26. It will be understood that the actuator 26 may be, for example, asolenoid which is interconnected with a more complicated exercisersystem in order to check the complete system and to prevent tripping theturbine inadvertently. The pressurized fluid of 200 p.s.i.

OPERATION The operation of the invention is as follows: Conventionaloverspeed tripping of the emergency governor 2 takes place when thespeed of the shaft is suflicient for the force on the center-of-mass 11of bolt 4 to overcome the bias of spring 6 whereupon the bolt movesoutward to strike trip lever 3.

To actuate the trip mechanism 3 without shaft I reaching an overspeedcondition, in accordance with the present invention, pressurized oil isadmitted to chamber 14 by opening valve 25. Oil flowing into theinterior of plunger 15 causes it to move to the right and to maintain itagainst the face 9 of the shaft end while oil continues to flow throughorifice 20. The pressure drop across the orifice maintains adifferential force which holds the plunger 15 in place. This is trueeven after the cavity 7 in the governor has been filled, due to slightleakage flow.

The oil pressure in cavity 7 acts against piston portion 10 ofoff-center bolt 4 to assist the off-center force which is also acting onthe bolt center of mass 11. This causes the bolt to move outward andactuate trip mechanism 3.

An oil film is maintained between surfaces 9, 21 by viscous pumping flowdue to rotation of the shaft end. Additional flow for this purpose maybe provided by the small holes 24 in the plunger. This oil film acts tolubricate the surfaces to prevent wear.

For resetting, valve 25 is closed. As the pressure in cavity 14 isreduced, spring 18 will retract injector plunger 15. As oil drains fromcavity 7 of the shaft, bolt 4 assumes its previous seated position.

Since the exercising of the governor is accomplished by pressure of theinjected fluid, rather than by eccentric mass of the fluid as inprevious devices, exercise of the governor is not wholly dependent uponspeed of rotation. Therefore, exercise can take place at low speeds aswell as high, which is desirable in variable speed applications.

While the embodiment shown has been designed for liquid or hydraulicfluid, it is also within the scope of the present invention tosubstitute air or pneumatic fluids to test the trip mechanism. Also amodification of the invention could include introduction of pressurizedfluid from the shaft periphery rather than from the shaft axis.

The present arrangement, however, is very successful because of thelubricating and sealing functions performed by the hydraulic fluid atthe shaft end.

What I claim is:

1. An emergency governor exerciser comprising:

a governor including a rotatable shaft portion defining a chamber withan inlet port and having an off-center member disposed therein withmeans biasing said member toward a seated position, said member beingradially movable to a tripping position and having a piston portionthereon disposed to assist said movement when the chamber ispressurized,

injector means for selectively pressurizing the chamber to exercise saidgovernor, said injector means comprising a plunger member coaxial withthe shaft and axially movable in response to receipt of pressurizedfluid and having an orificed outlet arranged to cover said shaft portioninlet port and inject pressurized fluid into said chamber when theplunger moves.

2. The combination according to claim 1, wherein said shaft portioninlet port comprises a shaft centerline hole and wherein said plungermember defines a flat face movable'to cover both the inlet hole and aportion of the shaft end, said face defining a slot extending beyondthe. inlet hole and supplied with pressurized fluid from the orifice tolubricate the interface between plunger'and shaft.

3. The combination according to claim 1, including second biasing meansretracting said plunger when pressurized fluid is cut off, saidretracting movement of the plunger acting to uncover the shaft portioninlet port, whereby the chamber pressure is reduced and oil drained toallow the off-center member to return to a seated position. 1 t

4. An emergency governor exerciser comprising:

a governor including a rotatable shaft portion defining a chamber withan inlet port and having an off-center member disposed therein withmeans biasing said member toward a seated position, said member beingradially movable to a tripping position and having a piston portionthereon disposed to assist said movement when the chamber ispressurized,

a source of hydraulic fluid under pressure,

a stationary body defining a second chamber arranged to selectivelyreceive hydraulic fluid from said source and having a plunger memberdisposed therein coaxial with the shaft portion,

second means biasing said plunger member to a retracted seating positionaxial spaced from the shaft portion, said plunger defining an orificecoaxial with the shaft centerline,

said plunger face defining a slot supplied by the orifice and extendingbeyond the shaft inlet port, whereby introduction of pressurizedhydraulic fluid will cause the plunger to move axially to supply fluidthrough said inlet port to exercise the emergency governor, said fluidalso flowing radially outward between the plunger face and the shaft endto lubricate the interface between members.

References Cited UNITED STATES PATENTS 1,441,353 1/1923 Johnson 137-241,621,084 3/1927 Rigsby 137-24 1,622,100 3/ 1927 Flanders 137-24 X1,623,822 4/1927 Wilkinson 137-24 X 1,666,490 4/ 1928 Dryer 137-241,756,850 4/1930 Caughey 137-24 1,970,420 8/1934 Floret 137-24 XCLARENCE R. GORDON, Primary Examiner' I US. 01. X.R. 73 54s; 137-798;2s1 14 s; 415-16

